Lack of access to appropriate sanitary products undermines efforts to create sustainable improvements in global human and environmental well-being, significantly impacting gender equality, social & civil empowerment, & human rights. Developed in collaboration with girls, the BeGirl Panties & FlexiPads deliver on every axis of need. As a beautiful, reusable menstrual product, it is washable & leak-proof with a permeable mesh pouch that can be filled with any safe reusable or disposable absorbent material. Beyond adapting to the available resources, the pouch can be filled to match volume of her unique flow making it the first “open source” menstrual product. It preserves privacy & the environment without compromising hygiene by replacing 125+ disposable sanitary pads, using 70% less water to wash than cloth pads, & drying indoors within an hour. The underwear form bypasses the stigma of sanitary products & sidesteps cultural barriers leading to widespread acceptance & use.